Power Module Junction Temperature Estimation for Low-Speed Motor Drives
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Solution Overview
Problem
Existing technologies struggle to accurately estimate the junction temperature of power modules in inverters when motors are driven at low speeds, leading to potential overheating and excessive stress due to temperature ripples.
Innovation Solution
A device and method using thermal models, specifically RC filters, to estimate junction temperature by determining conduction loss ripples and incorporating coolant temperature, allowing precise estimation of junction temperature during low-speed motor operation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If the motor is driven at low speed, then the power module generates heat due to conduction loss, but temperature ripples occur causing overtemperature and excessive stress
Solution Approach 1:
The patent applies preliminary action by estimating the junction temperature in advance using a thermal model before the overtemperature condition actually occurs. The controller calculates temperature ripples based on conduction loss ripples and coolant temperature, then performs derating proactively to prevent excessive stress on the power module during low-speed operation
Solution Approach 2:
The patent implements feedback by continuously monitoring the junction temperature estimation and using it to adjust the driving duty cycle. The controller receives feedback from the thermal model about temperature ripples and modifies the PWM duty cycle accordingly to maintain safe operating temperatures during low-speed motor operation
2Device complexity
If existing temperature estimation methods are used, then the estimation is simple, but the accuracy is insufficient leading to potential overheating
Solution Approach 1:
The patent applies parameter changes by incorporating multiple dynamic parameters into the temperature estimation: conduction loss ripples, coolant temperature variations, and thermal model parameters. This multi-parameter approach significantly improves estimation accuracy compared to simple fixed-temperature methods, while the computational complexity remains manageable through efficient thermal model implementation
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
Accurately estimates junction temperature of power modules during low-speed motor operation, preventing overheating and enabling effective derating to prevent device failure.
Implementation Method 1
The temperature ripple of the power module may be estimated from the ripple of the maximum conduction loss
Implementation Method 2
the amount of change in the junction temperature of the power module at the time of high-speed driving of the motor may be a value obtained by multiplying power loss during the high-speed driving of the motor by thermal resistance
Implementation Method 3
The thermal model may be an RC filter in which a resistor and a capacitor are connected in parallel, and may be a model in which the RC filter is provided as at least two RC filters connected in series
Data Source
AI summary
A device for estimating a junction temperature of a power module at time of low-speed driving of a motor includes one or more processors, and a storage medium operatively connected to the one or more processors and storing computer-readable instructions. When computer-readable instructions are executed by one or more processors, one or more processors are configured to determine a ripple of a maximum conduction loss due to conduction of power module at time of low-speed driving of motor, estimate a temperature ripple of power module from ripple of maximum conduction loss, and estimate junction temperature of power module by adding a junction temperature change of power module at time of high-speed driving of motor and a temperature of a coolant for cooling power module to temperature ripple. Temperature ripple of power module is estimated using a thermal model.